This invention relates to a multi-cylinder engine with a turbo-charger and more particularly to an improved turbo-charger arrangement for a multi-cylinder engine, particularly of the two-cycle type, as adapted to be embodied in an outboard motor.
The use of turbo-chargers as a method for increasing the power output of internal combustion engines is well known. Turbo-chargers are frequently used, for example, in connection with two-cycle, crankcase compression internal combustion engines so as to improve the scavenging and to increase the specific output of the engine. When a multi-cylinder engine is turbo-charged, it has been the practice to provide the turbine stage inlet to the exhaust conduit at a point that is only just slightly downstream of the place where the forwardmost exhaust port discharges into this conduit. This means that the exhaust gases from the remaining cylinders must flow in a reverse direction through the exhaust conduit in order to enter the turbine stage inlet. FIG. 1 of the drawings is an illustration of the prior art type of construction and depicts the conventional type of system.
Referring specifically to FIG. 1, a multi-cylinder, turbo-charged internal combustion engine constructed in accordance with the prior art is identified generally by the reference numeral 11 and is shown schematically. The engine 11 may operate on the two-stroke, crankcase compression principle. The engine 11 is of the multiple cylinder type and has at least certain of its cylinders in an aligned relationship. Such cylinders are depicted at 12, 13 and 14. The cylinders 12, 13 and 14 have respective exhaust ports that discharge their exhaust gases into pipes 15, 16 and 17 which curve in a rearward direction of the engine and which merge into a common collector exhaust conduit 18.
The engine 11 is also provided with a turbo-charger, indicated generally by the reference numeral 19 which includes a compressive stage 21 having an air inlet 22 and a compressed air outlet 23. The compressor stage 21 is driven by an exhaust turbine stage 24 which has an exhaust inlet 25 and an exhaust outlet 26.
With the conventional prior art type of engine, the exhaust gas inlet 25 of the turbine stage 24 communicates with the exhaust pipe 18 immediately downwardly of the point where the exhaust pipe 15 of the first cylinder 12 communicates with the exhaust conduit 18. That is, the turbine stage inlet 25 communicates with the exhaust conduit 18 upstream of the point where the cylinder exhaust pipes 16 and 17 communicate with it. Therefore, the exhaust gases must flow in a reverse direction through the exhaust pipe 18 as shown in FIG. 1 in order to enter the turbine stage inlet 25. Thus, the conventional type of engine does not provide the maximum amount of driving force for the turbine stage of the turbo-charger.
It is, therefore, a principal object of this invention to provide an improved driving arrangement for the turbo-charger of a turbo-charged engine.
It is a further object of this invention to provide an improved arrangement for communicating the exhaust gases of a multiple cylinder engine with the exhaust gas inlet of the turbine stage of a turbo-charger.
In addition to the problem of providing an appropriate and effective exhaust gas inlet for the turbine stage of a turbo-charger, the design of turbo-charged engines presents a number of difficulties with respect to the location of various components. For example, it is desirable to provide the compressor stage at a close location to its driving turbine stage. However, the heated exhaust gases of the turbine stage, if they are permitted to heat the compressor stage, can decrease the volumetric efficiency of the turbo-charger and reduce the maximum power output of the engine.
Also, it is well known that turbo-charged engines have throttle lag. That is, when the operator opens the throttle valve, there is a delay before the boost comes on due to the inertia of the turbo-charger and the fact that the exhaust gases do not accelerate the turbine stage as fast as the throttle has been opened. One well known method of reducing the amount of such throttle lag is to use multiple turbo-chargers. However, the use of multiple turbo-chargers further complicates the problem of locating all of the components and still maintaining a compact overall arrangement.
One large volume application for two-cycle internal combustion engines is in outboard motors. In such outboard motors, there is also a desire to increase the performance of the outboard motor and turbo-charging offers such an alternative. However, the space problems aforenoted are even more acute in an outboard motor due to its very compact nature. Also, the problem of heat transfer between the turbine stages and the compressor stages, particularly when multiple turbo-charges are employed, is even more acute in an outboard motor than in other applications.
It is, therefore, a further object of this invention to provide a compact and highly effective multiple turbo-charging arrangement for a multiple cylinder internal combustion engine.
It is a further object of this invention to provide an improved arrangement for turbo-charging an outboard motor.
It is a yet further object of this invention to provide an improved and compact arrangement for providing multiple turbo-chargers for an internal combustion engine.